全文获取类型
收费全文 | 417篇 |
免费 | 16篇 |
国内免费 | 6篇 |
专业分类
化学 | 357篇 |
晶体学 | 4篇 |
数学 | 27篇 |
物理学 | 51篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2018年 | 4篇 |
2017年 | 2篇 |
2016年 | 10篇 |
2015年 | 13篇 |
2014年 | 6篇 |
2013年 | 23篇 |
2012年 | 11篇 |
2011年 | 24篇 |
2010年 | 11篇 |
2009年 | 12篇 |
2008年 | 28篇 |
2007年 | 28篇 |
2006年 | 33篇 |
2005年 | 29篇 |
2004年 | 32篇 |
2003年 | 24篇 |
2002年 | 28篇 |
2001年 | 7篇 |
2000年 | 5篇 |
1999年 | 7篇 |
1998年 | 10篇 |
1997年 | 6篇 |
1996年 | 9篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 3篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1973年 | 5篇 |
排序方式: 共有439条查询结果,搜索用时 15 毫秒
121.
Fujiwara K Watarai H Itoh H Nakahama E Ogawa N 《Analytical and bioanalytical chemistry》2006,386(3):639-644
Antibody binding to bovine serum albumin (BSA) and human serum albumin (HSA) immobilized onto gold nanoparticles was studied
by means of localized surface plasmon resonance (LSPR) spectroscopy. Amine-modified glass was prepared by self-assembly of
amine-terminated silane on substrate, and gold (Au) nanoparticles were deposited on the amine-modified glass substrate. Au
nanoparticles deposited on the glass surface were functionalized by BSA and HSA. BSA immobilization was confirmed by LSPR
spectroscopy in conjunction with surface-enhanced Raman scattering spectroscopy. Then, LSPR response attributable to the binding
of anti-BSA and anti-HSA to BSA- and HSA-functionalized Au nanoparticles, respectively, was examined. Anti-HSA at levels larger
than ∼10 nM could be detected by HSA-immobilized chips with LSPR optical response, which was saturated at concentrations greater
than ∼650 nM of anti-HSA.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible to authorized
users. 相似文献
122.
The purpose of this study was to examine the potential of diffusion-weighted (DW) three-dimensional (3D) MP-RAGE MRI for diffusion-tensor mapping of the rat brain in vivo. A DW-3D-MP-RAGE (3D-DWI) sequence was implemented at 2.0 T using six gradient orientations and a b value of 1000 s/mm2. In this sequence, the preparation sequence with a "90 degrees RF-motion proving gradient (MPG): MPG-180 degrees RF-MPG-90 degrees RF" pulse train (DW driven equilibrium Fourier transform) was used to sensitize the magnetization to diffusion. A centric k-space acquisition order was necessary to minimize saturation effects (T1 contamination) from tissues with short relaxation time. The image matrix was 128x128x128 (interpolated from 64x64x64 acquisitions), which resulted in small isotropic DW image data (voxel size: 0.273x0.273x0.273 mm3). Moreover, 3D-DWI-derived maps of the fractional anisotropy (FA), relative anisotropy (RA) and main-diffusion direction were completely free of susceptibility-induced signal losses and geometric distortions. Two well-known commissural fibers, the corpus callosum and anterior commissure, were indicated and shown to be in agreement with the locations of these known stereotaxic atlases. The experiment took 45 min, and shorter times should be possible in clinical application. The 3D-DWI sequence allows for in vivo 3D diffusion-tensor mapping of the rat brain without motion artifacts and susceptibility to distortion. 相似文献
123.
Kohta Yamada Nobuaki Sato Takeo Fujino Choong G. Lee Isama Uchida Jan R. Selman 《Journal of Solid State Electrochemistry》1999,3(3):148-153
Syntheses of LiNiO2, LiCo0.5Ni0.5O2, and LiAl0.25Ni0.75O2 as thin films were carried out by electrostatic spray deposition (ESD) onto a gold substrate. Single-phase LiNiO2 film was obtained using a precursor solution of Li(OCOCH3)+Ni(OCOCH3)2/ethanol, and by heating the deposit at 700 °C under an oxygen stream. In the case of cobalt or aluminum doping, Co(NO3)2/ethanol or Al(NO3)3/ethanol were added to the precursor solution in a given ratio. X-ray diffractometry revealed that all films had a crystal
structure of space group R3ˉm; a=2.879, c=14.197 ? for LiNiO2; a=2.844, c=14.152 ? for LiCo0.5Ni0.5O2; a=2.855, c=14.148 ? for LiAl0.25Ni0.75O2 (in hexagonal setting). Although these products were highly porous, it was observed that the average film thickness of LiNiO2 increased almost proportionally with the deposition time. Electrochemical measurements (cyclic voltammetry, charge/discharge
measurement at a constant current) were carried out in organic solutions of LiClO4 (1 mol dm−3 LiClO4/propylene carbonate+ethylene carbonate). The results indicated that thin films fabricated by ESD were electrochemically active
for lithium ion extraction/insertion. The effect of cobalt or aluminum doping on the voltammograms is also described.
Received: 1 April 1998 / Accepted: 23 July 1998 相似文献
124.
Studies on the structures and dynamic behaviors of electron donor-acceptor(EDA) systems in the excited state (such as exciplexes and excited EDA complexes which are stable also in the ground state) are important for understanding primary processes of some photochemical and photobiological reactions, especially photo-oxidationreduction reactions. 相似文献
125.
Glycotentacles: synthesis of cyclic glycopeptides, toward a tailored blocker of influenza virus hemagglutinin 总被引:1,自引:0,他引:1
126.
Tsembel Darjaa Kohta Yamada Nobuaki Sato T. Fujino Yoshio Waseda 《Fresenius' Journal of Analytical Chemistry》1998,361(5):442-444
The sulfur content in metal sulfides can be determined after oxidative dissolution with bromine water-CCl4 at 50 °C by modified EDTA titration. The sulfides were quantitatively oxidized to SO4
2– without evolving H2S, and the metal cations were removed by cation exchange on an H-type column. Sulfate was precipitated as BaSO4, and the remaining Ba2+ was subsequently titrated with EDTA at pH = 10. The standard deviation for the determined sulfur in the metal sulfides, some
of which can be hardly dissolved in usual mineral acid media, is about a few %. The method can be carried out with sample
amounts containing as little as 1.5–2 mg sulfur.
Received: 31 July 1997 / Revised: 5 January 1998 / Accepted: 9 January 1998 相似文献
127.
Koike K Okoshi N Hori H Takeuchi K Ishitani O Tsubaki H Clark IP George MW Johnson FP Turner JJ 《Journal of the American Chemical Society》2002,124(38):11448-11455
We report herein the mechanism of the photochemical ligand substitution reactions of a series of fac-[Re(X(2)bpy)(CO)(3)(PR(3))](+) complexes (1) and the properties of their triplet ligand-field ((3)LF) excited states. The reason for the photostability of the rhenium complexes [Re(X(2)bpy)(CO)(3)(py)](+) (3) and [Re(X(2)bpy)(CO)(3)Cl] (4) was also investigated. Irradiation of an acetonitrile solution of 1 selectively gave the biscarbonyl complexes cis,trans-[Re(X(2)bpy)(CO)(2)(PR(3))(CH(3)CN)](+) (2). Isotope experiments clearly showed that the CO ligand trans to the PR(3) ligand was selectively substituted. The photochemical reactions proceeded via a dissociative mechanism from the (3)LF excited state. The thermodynamical data for the (3)LF excited states of complexes 1 and the corrective nonradiative decay rate constants for the triplet metal-to-ligand charge-transfer ((3)MLCT) states were obtained from temperature-dependence data for the emission lifetimes and for the quantum yields of the photochemical reactions and the emission. Comparison of 1 with [Re(X(2)bpy)(CO)(3)(py)](+) (3) and [Re(X(2)bpy)(CO)(3)Cl] (4) indicated that the (3)LF states of some 3- and 4-type complexes are probably accessible from the (3)MLCT state even at ambient temperature, but these complexes were stable to irradiation at 365 nm. The photostability of 3 and 4, in contrast to 1, can be explained by differences in the trans effects of the PR(3), py, and Cl(-) ligands. 相似文献
128.
Shimada Y Taniguchi N Matsuhisa A Yatsu T Tahara A Tanaka A 《Chemical & pharmaceutical bulletin》2003,51(9):1075-1080
A series of compounds structurally related to 4'-[(4,4-difluoro-5-methylidene-2,3,4,5-tetrahydro-1H-1-benzoazepin-1-yl)carbonyl]benzanilide were synthesized and evaluated for arginine vasopressin (AVP) antagonistic activity. Compounds with alkoxy groups (especially ethoxy group) at the 2'-position of benzanilide possessed potent affinity and selectivity for the V1A receptor versus V2 receptor. Further study has shown that the introduction of 4,4-dimethylaminopiperidino and morpholino groups at carbonylmethylene exhibited more potent affinity and selectivity for V1A receptors. Consequently, we found that the (Z)-4'-([4,4-Difluoro-5-[(4-dimethylaminopiperidino)carbonylmethylene]-2,3,4,5-tetrahydro-1H-1-benzoazepin-1-yl]carbonyl)-2-ethoxybenzanilide monohydrochloride (8d) and the (Z)-4'-[(4,4-Difluoro-5-morpholinocarbamoylethylene-2,3,4,5-tetrahydro-1H-1-benzoazepin-1-yl)carbonyl]-2-ethoxybenzanilide (8q) exhibited potent and selective V1A receptor antagonist activity. The synthesis and pharmacological properties of these compounds are detailed in this paper. 相似文献
129.
Hiromasa Nishikiori Nobuaki Tanaka Katsuhiko Takagi Tsuneo Fujii 《Research on Chemical Intermediates》2003,29(5):485-493
Fluorescence and excitation spectra of spironaphthoxazine (SNO) in various solvents have been investigated systematically. The fluorescence in low-polar solvents normally originated from SNO in the excited state. In protic high-polar solvents, fluorescence from an excited intermediate species (X*
h) relaxed from a part of the excited SNO by breaking a C-O bond in the oxazine ring was also observed. It has been found that a ground-state intermediate species (Xs), transformed from a part of ground-state SNO, is directly excited to its excited state (Xs
*), which displays fluorescence in aprotic high-polar solvents. 相似文献
130.
Described is an efficient synthesis of the complex bioactive natural product, elisapterosin B, a potent in vitro inhibitor of Mycobacterium tuberculosis H37Rb. The synthesis elisapterosin B, prepared in its enantiomeric form, proceeds by a highly stereocontrolled sequence commencing with a simple glutamic acid derived compound. Pivotal steps in the sequence include (a) a pinacol-type ketal rearrangement to transfer chirality, (b) an IMDA reaction of an E,Z-diene to construct the elisabethin skeleton, and (c) a biosynthesis-inspired oxidative cyclization of the elisabethin precursor to elisapterosin B. 相似文献